While building mu-metal, permalloy, shielded rooms is challanging anyway, designing and building mu-metal shielded room inside a clean room environment is a task itself. To meet clean room class 3 specifications, material must not only be clean, but must be of clean room compatible material, too.
In this special mask writer application, the tool itself is completely housed inside the shielded room, sitting on a concrete foundation. However, the feeders remain accessible from outside of the shielded room, maintaining completely unimpeded access. This special "feeder integrated" shielding design was developped by Systron and is used for applications with very high requirements regarding attenuation of the shielding, cleanlyness of the room and servicability of the tool. Feeder integrated shielding design